With the increasing movement of oil over the world's oceans, there has developed a need for ever larger tankers to move the oil. Increase in tanker size presents a number of problems, including structural problems of designing the vessel to withstand the surface wave action encountered, the docking problem difficulties in loading and unloading, and maneuvering over existing navigable waterways. While the use of barges or floating cargo containers has been proposed to permit existing tankers to effectively increase their capacity, towing at sea is a hazardous undertaking. Conventionally the tow lines must be made relatively long to permit damping of the relative movement between the two vessels, and give the barge room to maneuver without colliding with the towing vessel. Also, the barge or container must be far enough back to be outside the influence of the propeller wake of the towing vessel.